Field fertility of frozen-thawed boar sperm at low doses using non-surgical, deep uterine insemination

The lowest dose of frozen-thawed boar sperm used for deep uterine artificial insemination (DUI) of sows has been 100 × 106. A three stage field study was performed to establish to what level the dose of frozen-thawed sperm used for DUI could be reduced without adversely affecting the fertility of the sow. In stage 1, 15 sows were inseminated twice with 1000 × 106 fresh or frozen-thawed sperm at 24 and 36 h post-detection of oestrus. In stage 2, 262 sows were inseminated with 62.5, 250 or 1000 × 106 fresh or frozen-thawed sperm at 24, 36, or 24 and 36 h after detection of oestrus. Stage 3 involved post mortem investigation of the uterine lining to assess damage caused by insertion of the insemination catheter. All sows inseminated in stage 1 of the study farrowed. In stage 2, the non-return (NRR) and farrowing rates of each group were compared to a control double cervical insemination of 3250 × 106 fresh sperm. As few as 62.5 × 106 fresh sperm could be deposited at a single insemination without reduction in NRR or farrowing rates compared with the control group. A double DUI with 250 × 106 frozen-thawed sperm was required before fertility was equivalent to the controls. Investigation of the uterine lining after insertion of the DUI catheter revealed evidence of bleeding, warranting further investigation of the viability of widespread use of the Firflex® catheter, despite the promising fertility achieved here with low doses of spermatozoa.